Well, to be honest: no, I didn't recognize monkeys or romans - I thought the first wave of enemies were turtles :D
But don't lose hope, creating nice art is really hard, especially if you only have 3 hours. I suck at art and it's taking me forever. One thing you can do is to use free assets for rapid prototyping, or team up with an actual game artist. I participated with an artist in the last Ludum Dare, it's amazing how fast they get things done.